IMHO, if one is a small business in which one must wear many hats, one should have a business model which is based on 20-25 hours of paid work rather than 40 (unless you thinking working to burn out is a productive business model).
Depending on that hats you wear you need time for:
Marketing
Sales
Equipment Maintenance
Education/training
Accounting
Evaluating potential purchases
Just to name a few things off the top of my head. Keep in mind that 20-25/hrs must cover the cost of purchasing and maintaining equipment and software, office supplies, housing, food, utilities, insurance (both health and business), investment in business growth, personal luxuries to keep you sane an motivated.
I won’t claim I’m successful at managing all the above but that’s the goal. Set your rates too low and your setting yourself up for a failed business or burn out.